ORDER_VAR = 'o'
ORDER_TYPE_VAR = 'ot'
class SortHeaders:
"""
Handles generation of an argument for the Django ORM's
``order_by`` method and generation of table headers which reflect
the currently selected sort, based on defined table headers with
matching sort criteria.
Based in part on the Django Admin application's ``ChangeList``
functionality.
"""
def __init__(self, request, headers, default_order_field=None,
default_order_type='asc', additional_params=None):
"""
request
The request currently being processed - the current sort
order field and type are determined based on GET
parameters.
headers
A list of two-tuples of header text and matching ordering
criteria for use with the Django ORM's ``order_by``
method. A criterion of ``None`` indicates that a header
is not sortable.
default_order_field
The index of the header definition to be used for default
ordering and when an invalid or non-sortable header is
specified in GET parameters. If not specified, the index
of the first sortable header will be used.
default_order_type
The default type of ordering used - must be one of
``'asc`` or ``'desc'``.
additional_params:
Query parameters which should always appear in sort links,
specified as a dictionary mapping parameter names to
values. For example, this might contain the current page
number if you're sorting a paginated list of items.
"""
if default_order_field is None:
for i, (header, query_lookup) in enumerate(headers):
if query_lookup is not None:
default_order_field = i
break
if default_order_field is None:
raise AttributeError('No default_order_field was specified and none of the header definitions given were sortable.')
if default_order_type not in ('asc', 'desc'):
raise AttributeError('If given, default_order_type must be one of \'asc\' or \'desc\'.')
if additional_params is None: additional_params = {}
self.header_defs = headers
self.additional_params = additional_params
self.order_field, self.order_type = default_order_field, default_order_type
# Determine order field and order type for the current request
params = dict(request.GET.items())
if ORDER_VAR in params:
try:
new_order_field = int(params[ORDER_VAR])
if headers[new_order_field][1] is not None:
self.order_field = new_order_field
except (IndexError, ValueError):
pass # Use the default
if ORDER_TYPE_VAR in params and params[ORDER_TYPE_VAR] in ('asc', 'desc'):
self.order_type = params[ORDER_TYPE_VAR]
def headers(self):
"""
Generates dicts containing header and sort link details for
all defined headers.
"""
for i, (header, order_criterion) in enumerate(self.header_defs):
th_classes = []
new_order_type = 'asc'
if i == self.order_field:
th_classes.append('sorted %sending' % self.order_type)
new_order_type = {'asc': 'desc', 'desc': 'asc'}[self.order_type]
yield {
'text': header,
'sortable': order_criterion is not None,
'url': self.get_query_string({ORDER_VAR: i, ORDER_TYPE_VAR: new_order_type}),
'class_attr': (th_classes and ' class="%s"' % ' '.join(th_classes) or ''),
}
def get_query_string(self, params):
"""
Creates a query string from the given dictionary of
parameters, including any additonal parameters which should
always be present.
"""
params.update(self.additional_params)
return '?%s' % '&'.join(['%s=%s' % (param, value) \
for param, value in params.items()])
def get_order_by(self):
"""
Creates an ordering criterion based on the current order
field and order type, for use with the Django ORM's
``order_by`` method.
"""
return '%s%s' % (
self.order_type == 'desc' and '-' or '',
self.header_defs[self.order_field][1],
)